Electrical connectors for printed circuit boards typically have a plurality of contact terminals therein to electrically engage respective electrical conductors along the surface of the board. Such electrical engagement is most commonly made by one of two methods: the terminals may have pin portions extending outward from the connector to be inserted into and through plated through-holes of the board where plating material on inside walls of the holes makes electrical connection to conductors on the board surface; or, the terminals may have leg portions extending substantially parallel to the board surface along and against the conductors on the board surface. In both cases the electrical engagement is commonly assured by soldering the electrical connection of the pin portions to the board conductors or plating material, or the leg portions to the board conductors.
In either method of making the electrical connection, the electrical connector is mechanically secured to the printed circuit board by means of clamping screws extending through holes drilled through the board and bolted on the opposing surface, such as is disclosed in U.S. Pat. No. 4,087,146, by rivets as disclosed in U.S. Pat. No. 4,401,355, by brackets such as disclosed in U.S. patent application Ser. No. 683,538 having pins which wedge in such drilled holes and may be soldered, or by latching mounting legs as disclosed in U.S. Pat. No. 4,439,000. The electrical connector may be held to the board by a separate shroud which is secured to the board in the manner just described, or in a manner such as is disclosed in U.S. Pat. No. 4,173,387.
It is also known that an electrical connector secured firmly to a board by such means and whose terminals have leg portions to engage surface conductors, need not necessarily require soldering of the terminal leg portions to the conductors but instead rely on the connector securing means to hold the connector and its terminal leg portions firmly against the conductors with the leg portions being spring-biased against the respective conductors, as in U.S. Pat. No. 4,087,146.
The drive toward surface mount technology reflects the desire to miniaturize electrical devices, components, and connectors and the board to which they are mounted. Eliminating plated through-holes enabled much closer spacing of terminals in a connector, and therefore, smaller connectors. Electrical components having, for instance, only a relatively few leads can be adequately secured to the surface simply by soldering. Such a component is not subjected to the mating and unmating forces of a multiterminal connector with a mating connector. But a connector would have to be secured by means other than only soldering its terminals to board conductors to withstand such forces.
During soldering of a connector to a board where significant heat is applied, and also during in-service functioning of such a printed circuit board having a connector secured thereto where in-service temperatures may achieve significant levels such as 125 degrees Celsius, the rate of temperature rise and fall may typically be rapid. A connector made of a certain dielectric material with a specific structure and mass distribution has a certain first coefficient of thermal expansion, and the printed circuit board of a certain material and different, planar structure has a certain second coefficient of thermal expansion usually substantially different from that of the connector. With significant amounts and rapid rates of temperature changes, the differences in such coefficients of thermal expansion result in expansion and contraction of the connector and the board relative to each other, or such differences result at least in stresses thereon.
It is therefore desirable to provide a means for securing an electrical connector to a printed circuit board which allows for expansion and contraction of a connector relative to the board, and which does not impose significant stress on the soldered electrical connections of terminals to board conductors as a result of such expansion and contraction.
It is also desirable to provide a means for securing a connector to a board which resists the mating and unmating forces of another connector being mated and unmated with the connector secured to the board.
It is further desirable to provide a relatively simple and economical method of securing a connector to a board which eliminates the need for holes to be drilled or formed in the board.
It is additionally desirable to provide a securing method which can be performed simultaneously with the terminal soldering operation and also using the same materials.